bought him a car and he does this!‼️😡

Last week I bought my fiancé a new Mercedes Benz because his Honda got in a wreck a week before his birthday  (December 5.) he posted a pic on his fb of him leaning on his car with the bow still on it with the caption "best present ever" I commented "you're welcome babe😘" he deleted my comment after a few of his friends started commenting . Mind you its friends that only wanted rides when he had a car and didn't hit him up when he didn't have one. Anyways his ex commented "😍😍inbox me" he deleted her comment . I'm thinkn he dismissed her. Today after work he said he had to run errands for his mom this was around 2 my childhood best friend calls me like guess who she just seen him and her at her restaurant....he came back home at 6:42 , I confronted him bout him having his ex in the car I got him and being with her period. Then asked why he deleted our comments. He apologized for deleting mine and said I can put it back then he said he deleted hers cuz he knew I'd trip and he was with her cuz he wanted to show off. He said he'd block her and never see her again. I asked if all they did was go out to eat he admit to going to her place I started crying before he could even say they didn't do anything. He tried to reach out for me and I punched him then threw my ring at him. He shook his head said he fucked up . Then began packing his stuff. I'm like where do u think u going in my car and asked for the keys. Should I return it or should I let it go?
UPDATE: I'm going to return the car tomorrow thanks for everyone's suggestions! He called his ex saying how he can't see her anymore . Of course she was all like why🙄 he told her I knew and he don't wanna loose me. Ig she was mad n hung up. Then she messaged me on fb saying she just wanted to clear up that they didn't do anything. He helped her move some heavy boxes then said he had to go home to his girl. And that she understands. As for me and him we'll make 3 years in February . He's staying at his brothers house tonight but He needs to earn my trust again.